Strain-insulator.



G. P. BOLDMAN.

STRAIN INSULATOIL,

APPLICATION FILED APR.22, 1908,

938.409. Patented 0013.26, 1909.

INVENTOR WITNESSES:

mitten srntrns PATENT orrro CURTIS F. BOLIDMAN, OF CANTON, NORTH CAROLINA, ASSIGNOR, BY IVIESNE ASSIGN- MENTS, TO VJESTINGHOUSE ELEGTRIO &'MANUFACTURING COMPANY, OF EAST PITTSBURG, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

STRAIN-INSULATOR.

lators, of which the following is a specifica tion.

My invention relates to strain insulators for electric lines, and it has for its object to provide a device of this character that shall be especially compactand durable in construction and capable of withstanding strains incident to the use of high voltages.

It is awell known fact that porcelain and other hard insulating materialsare capable of sustaining, without injury, very largeforces in compression and that such sub stances are easily ruptured by comparatively small shearing or tensile strains.

According to my present invention, Ipro- 'vide a strain insulator which prevents surface leakage of electrical energy and the insulating parts of which are largely exempt from all but compression strains.

Figure l of the accompanying drawings is a sectional elevation of'a strain insulator constructed in accordance with my invention, and Fig. 2 is a detail perspective view of a portion of the device shown in Fig. 1. 5

Referring to the drawings, the strain insulator which is here illustrated, comprises a metal strain rod or bolt 1 to which a strain loop 2 is secured, an insulating sleeve or bushing 23 which is fitted loosely over the bolt or rod 1, a metal ring 4 which is clamped about the bushing intermediate its ends and forms a part of a clevis 5, an insulating cap 6 for protecting the inner end of the rod or bolt 1, and a strain loop 7 attached to the clevis 5.

The inner end of the bolt on rod 1 is provided with a headto engage the inner end of the sleeve or bushing 3., As here shown-,the head comprises a nuti'8 and a washer 9, but any other head of suitable character may be employed.

The insulating bushing 3 is rovided with an annular groove 10 to receive the metal ring of the clevis 5, and its outer surface between the ring and the strain loop 2 is corrugated to increase the surface distance be' Specification of Letters l atent.

Application filed April 22, 1908.

Patented Oct. 26, 1909. Serial No. 428,534.

tween these two metal parts which are electrically separated. The opposite end of the bushing is frusto-conical and is provided with an insulating cap 6 for the purpose of improving the insulation between the nut or enlargement 8 of the strain rod 1 and the side rods 11 and-l2 of the clevis, which are substantially parallel to the rod and are bent inwardly at their ends to form segments 13 of the ring 4.

In assembling the insulator, the two halves of the ring 4 are separated by springing the rods 11 and 12 of the clevis apart until the ring segments can be fitted into the groove 10. When in position, the ringsegments are fastened together by bolts 14. The cap 6 is held in position over the conical end of the insulator 3 by insulating cement or gum, annular grooves 15 and 16 being provided on the outer surface of the insulator and the inner surface of the cap, respectively, to provide a holding surface for the cement after it has hardened.

When tensile strains are exerted between the loops 2 and 7, that portion of the insulating bushing 3 which lies between the groove 10 and the nut or enlargement 8 is placed under compression, while the metal parts, including the clevis 5 and the strain rod 1, are subjected to tensile strain.

It will be understood that suitable cushioning means may be interposed between the metal parts and the adjacent surfaces of the co-acting insulating body, if desired.

It will be understood that various structural modifications may be .efiected within the spirit and scope of my invention.

' I claim as my invention:

1. A strain insulator comprising an, insulating sleeve, a strain rod extending completely through said sleeve and having a head or enlargement at one end, a strain member clamped around said sleeve intermediate its ends and an insulating cap fitted on to one end of said sleeve over said head or enlargement.

2. A strain insulator comprising a sleeve or bushing of hard ins lating material having an annular groove intermediate its ends, a strain rod extending through the sleeve and having a head at one end and astrain loop at the other, an insulating cap fitted over the end of the sleeve or bushing and subscribed my name this seventh day of the head, a clevis orclamp comprising a April, 1908.

se mental rlng encircling the insulating sleeve and disposed in said annular groove, CURTIS BOLDMAN' and a second strain loopprojecting from the Witnesses:

outer end of the clevis or clamp. N. J. FOREE,

In testimony Wherepf, I have hereunto H, SPRAY. 

